June 20, 2013
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Corneal correction formula allows IOL power calculation without pre-LASIK data

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A corneal correction equation for the Shammas post-hyperopic LASIK formula can be used to calculate IOL power in cases in which preoperative LASIK data are not available, according to a study.

The retrospective, comparative observational study comprised 42 eyes: 18 eyes with pre-LASIK and post-LASIK data with keratometric readings and stable refractions, and 24 eyes with no pre-LASIK data.

Using the formula, the eyes with pre-LASIK data had a mean arithmetic prediction error of –0.03 ± 0.72 D (range: –1.57 D to +1.54 D) and a median absolute error of 0.38 D. The eyes with no pre-LASIK data had a mean arithmetic prediction of 0.05 ± 0.58 D (range: –0.56 D to +1.4 D) and a median absolute error of 0.43 D.

The arithmetic and absolute errors were among the lowest for the Shammas-PHL formula compared with seven other formulas available on the American Society of Cataract and Refractive Surgery website, the study authors said.